μcaptcha FAQ

What is μcaptcha?

μcaptcha is a math handwriting captcha scheme for touch-capable
devices. Instead of entering text with a keyboard, you just retype a
mathematical expression shown on a web canvas.
μcaptcha belongs to the set of protocols called
HIPs (Human Interactive Proofs), which allow a person to authenticate as
belonging to a select group; e.g., human as opposed to machine, adult as
opposed to a child, etc.

Why yet another captcha?

Solving captchas on a mobile device is rather uncomfortable.
The vast majority of captchas are designed for use on computers and laptops,
which do not align well with the interaction style of mobile users.
Other alternatives are either poorly usable, insecure or not scalable.
Our studies
reveal that μcaptcha is accurate, fast, and easy to perform,
and that users find it to be both useful and enjoyable.

How does μcaptcha work?

A mobile user is presented with a random μcaptcha challenge that has a unique ID.
When the user retypes the challenge, a sequence of handwritten strokes are generated.
Both the ID and the handwritten strokes are populated to the μcaptcha-protected form,
so that when the form is submitted a math recognizer verifies the challenge under the hoods.
In short, for a challenge to be passed, the handwritten strokes must match the challenge ID after verification.

Does μcaptcha work for non-mobile users?

Does μcaptcha work for blind users?

Not currently, though we plan to offer an audio-based version in the future.
We implemented it a while ago, but we felt it was not ready for production use.

Does μcaptcha work for users with JavaScript disabled?

No, and in fact most spam bots don't execute JavaScript.
We personally recommend combining some honeypot technique
with μcaptcha to achieve the most satisfactory results.

How much does μcaptcha cost?

The service is currently free for anyone to use.
Just register and start using μcaptcha on your website.
And if you want to become an official μcaptcha service provider,
contact us and we will discuss the best fares for you.